"Nigel Marven, a time-traveling zoologist, and a man who has had his fair share of close scrapes with dinosaurs. But the Earth has witnessed more terrible monsters then these. What Nigel is about to learn about prehistory, is that no matter how bad things get on land, the one thing you should never, ever do... Is get in the water."
— Narration of the prologue of the first episode.
Sea Monsters: A Walking with Dinosaurs Trilogy is a 2003 series in the Speculative Documentary franchise Walking with…. Following the format set by the previous year's Chased by Dinosaurs specials, the series follows wildlife presenter Nigel Marven as he and his crew travel through time to the ancient seas of Earth's past. Counting down the seven most deadly seas, Nigel gets close and personal with the largest prehistoric predators to ever swim in the oceans. Using the latest in diving technology, Nigel experiences close-call after close-call as he tries to learn more about these extinct creatures.
In 2004, Sea Monsters would be bundled with the Chased by Dinosaurs specials into a DVD set simply titled Chased by Dinosaurs, with the former's title even changed to Chased by Sea Monsters on the DVD case.
If you are looking for the trope, see Sea Monster.
Tropes present include:
- Anachronistic Animal:
- The Mid Triassic segment, set 230 MYA, includes the giant ichthyosaur Cymbospondylus, but it is last known to have lived seven million years prior. Small theropods and small pterosaurs also appears in briefly on the coast, but no theropods or pterosaurs are known from the specific time and place (not stated, but considering the fauna, probably Central Europe) until about ten million years later.
- The Pliocene segment, set 4 MYA, includes the toothed whale Odobenocetops, but this animal is only known from the earlier Late Miocene, more than a million years earlier.
- Though placed in its proper environment this time (the Late Cretaceous Western Interior Seaway), Pteranodon is now 5 million years too late, with the youngest known fossils being 80 million years old, though pteranodontids of some kind would have likely still been here by 75 mya.
- T. rex appears in a cameo role 75 million years ago, whereas the oldest known rex dates from "only" about 68 million years ago. And it's clearly confirmed to be a real T. rex in the book, not one of its ancestors.note This is especially weird, since some of their earlier material has shown that the creators knew when the T. rex actually lived.
- Animal Reaction Shot: There's a scene where a mosasaur capsizes Nigel Marven's boat. Immediately afterwards, a Pteranodon that had taken up residence on his boat is seen shrieking in panic.
- Attention Deficit... Ooh, Shiny!: Nigel refuses to enter "Hell's Aquarium" because it's way too dangerous - but upon sight of a giant turtle, he jumps right in to ride one. This, after finding one of them bitten in half.
- Bloodier and Gorier: Due to the fact that most of the show happens in the water, blood is more visible in this series than in Chased by Dinosaurs.
- Bolivian Army Ending: During the credits of the last episode, a pod of mosasaurs is shown surrounding and approaching the crew's boat, but we don't find out if they survive.
- Color Motif: Each of the seas Nigel visits has a determinate hue to it, setting a particular mood and atmosphere on it distinct from each other. These are:
- The Ordovician: Dark blue
- The Triassic: Aquamarine
- The Devonian: Purple
- The Eocene: Blue
- The Pliocene: Green
- The Jurassic: Black
- The Cretaceous: Gray
- Darker and Edgier: Though still mostly a lighthearted adventure, compared with Chased by Dinosaurs, the tone of Sea Monsters is more serious and edgy than its predecessor, with Nigel being out of his element facing some of the most dangerous marine predators of the past in situations that put him at more risk than in the previous series and having several close encounters with death, with the ending implying he and his crew are attacked by a massive pod of Tylosaurus with presumably fatal results. This is also reflected in the soundtrack of the documentary, that sounds more menacing and oppressive compared to the more magical and grandiose one in Chased by Dinosaurs, with tracks that wouldn't be out of place in Jaws. Just compare the main theme of ''Chased by Dinosaurs''
with the one of ''Sea Monsters''. - Death World: While nearly all the seas could count, the Cretaceous Western Interior Seaway, which is actually called Hell's Aquarium to signify its dangers, particularly stands out.
- Feathered Fiend: Subverted with Hesperornis, which look aggressive but only serve to get eaten by other predators. Played straight in the book, which lists dromaeosaurs as Cretaceous land menaces.
- Fiendish Fish: Nigel explores the seven most dangerous seas in history. Two of the species he encounters are giant killer fish, Dunkleosteus and Xiphactinus.
- Fluffy Tamer: Nigel and his crew manage to get a Pteranodon to hang out on their boat. It seems to grow fond of them, given the fact that it appears to be genuinely shocked when it seems that Nigel's about to be eaten.
- Giant Flyer: The Pteranodons.
- Goddamn Bats: Nigel's opinion of the sea scorpions. While their claws can give you some nasty cuts, they generally aren't lethal enough to pose too much of a threat, so they mostly serve as a nuisance.
- Gosh Dang It to Heck!: In all of his near-misses with prehistoric monsters, Nigel's most coarse language amounts to "flipping heck!". At the begging of episode three, he apologizes for angrily calling a crew member an "idiot". Of course, he is presenting a wildlife series in-universe.
- Herbivores Are Friendly: Subverted by the Arsinoitherium, which charges Nigel when he gets too close.
- Historical Badass Upgrade: The colossal Liopleurodon makes a comeback, earning the Late Jurassic the title of "second deadliest sea ever". In reality, it was only slightly larger than a big great white, and would hardly hold a candle to megalodon, which gets ranked just below it.
- I Don't Like the Sound of That Place: No, really, "Hell's Aquarium". It more than deserves its title given the sheer number of superpredators roaming the seas at that time.
- Monster Whale: Basilosaurus. While it doesn't attack Nigel, the fact that it bites a speaker that plays sounds of a fellow Basilosaurus to give the impression of another whale in its territory is all the evidence you need that this whale is not one you want to go swimming with in open water.
- Monstrous Cannibalism: An adult Dunkleosteus is shown devouring a juvenile after the latter arrives to scavenge some leftovers of the larger predator's previous meal. Nigel also mentions that juvenile Megalodon stay as far away from the adults as possible so as not to risk becoming food.
- Perilous Prehistoric Seas: The series is naturally about these, from giant sea scorpions and cephalopods in the Ordovician period to mosasaurs of the Niobrara Sea (more commonly known as the Western Interior Seaway) in what's dubbed the Deadliest Seas of all time. Many of the creatures that Nigel encounters are actually quite docile, or at least uninterested in attacking him, and are more concerned with their own needs. While there are genuine threats like the Megalodon, Liopleurodon, and the Tylosaurus, this only ends up being the case whenever Nigel gets too close to them, otherwise, they are only hunting for their preferred prey and react in a way any other animal would. That said, in the end, a Tylosaurus family does cross into Prehistoric Monster territory by approaching and attacking Nigel's ship.
- Prehistoric Monster: Played straight, but that's kind of the point. Of course, they're also treated as simply animals, albeit dangerous ones, with Nigel going shark-cage diving with the Megalodon. He does so with Dunkleosteus as well, and the way the armored fish seriously bends the thick bars, it's strongly implied that Nigel isn't safe in it.
- Russian Reversal: Nigel notes in Hell's Aquarium that while Pteranodon would look for fish to catch, in these waters, sometimes the fish caught them.
- Schmuck Bait: Nigel repeatedly states that there's no way he would go into "Hell's Aquarium" - but decides to dive in anyway to ride a giant sea turtle.
- Sea Monster: The title should tell you something. The monsters in question are all progressively more lethal to humans, varying from giant sharks and other types of fish, to aquatic reptiles, a prehistoric whale, and even giant arthropods.
- The third most dangerous Sea Monster is the famous prehistoric shark. Nigel and his team decide it's safer to try swimming with one of the juveniles (already the size of a great white) in the shallows first before moving on to the humongous adults patrolling the oceans—and even then Nigel insists on using a reinforced cage.
- Sensor Suspense: The miniseries ends with the crew fast asleep on their ship in Hell's Aquarium while their sonar detects a huge family of mosasaur approaching them.
- The Stinger: A pod of mosasaurs attacks the boat after the credits for the last episode.
- Threatening Shark: C. megalodon; unusual given how often the series subverts this. Granted, the narration turns somber when it is described that once changing climates causing the whales that it preyed on to head north, the megalodon went extinct from starvation.
- The Unreveal: Like in Chased by Dinosaurs, the way Nigel travels back to prehistory is never shown. However, this time is vaguely implied that he employs the time map shown in the parts that introduce each new sea to travel to the time period he desires.
